Fixes issue with diff files added in index/working tree

src/commands/diffWith.ts

@@ -108,7 +108,8 @@ export class DiffWithCommand extends ActiveEditorCommand {
             if (args.lhs.sha !== GitService.deletedOrMissingSha) {
                 lhsSha = args.lhs.sha;
             }
-            if (args.rhs.sha !== GitService.deletedOrMissingSha) {
+
+            if (args.rhs.sha && args.rhs.sha !== GitService.deletedOrMissingSha) {
                 // Ensure that the file still exists in this commit
                 const status = await Container.git.getFileStatusForCommit(
                     args.repoPath,

src/git/git.ts

@@ -511,6 +511,8 @@ export class Git {
     }
 
     static async cat_file_validate(repoPath: string, fileName: string, ref: string) {
+        if (Git.isUncommitted(ref)) return ref;
+
         try {
             await git<string>(
                 { cwd: repoPath, exceptionHandler: throwExceptionHandler },

src/git/gitService.ts

@@ -1850,14 +1850,17 @@ export class GitService implements Disposable {
     }
 
     async resolveReference(repoPath: string, ref: string, uri?: Uri) {
-        if (Git.isSha(ref) || !Git.isShaLike(ref) || ref.endsWith('^3')) return ref;
-
         Logger.log(`resolveReference('${repoPath}', '${ref}', '${uri && uri.toString(true)}')`);
 
-        if (uri == null) return (await Git.revparse(repoPath, ref)) || ref;
+        const resolved = Git.isSha(ref) || !Git.isShaLike(ref) || ref.endsWith('^3');
+        if (uri == null) return resolved ? ref : (await Git.revparse(repoPath, ref)) || ref;
 
         const fileName = Strings.normalizePath(paths.relative(repoPath, uri.fsPath));
-        const resolvedRef = await Git.log_resolve(repoPath, fileName, ref);
+
+        let resolvedRef;
+        if (!resolved) {
+            resolvedRef = await Git.log_resolve(repoPath, fileName, ref);
+        }
 
         const ensuredRef = await Git.cat_file_validate(repoPath, fileName, resolvedRef || ref);
         if (ensuredRef === undefined) return ref;